Fix #200 - Use looseversion if pkg_resources doesn't work

CHANGELOG.md

@@ -1,5 +1,12 @@
 # Changelog for https://github.com/mbarkhau/bumpver
 
+## BumpVer 2023.1121
+
+- Fix [#200][gh_i200]: Fix compatability with packaging 23.0.
+
+[gh_i200]: https://github.com/mbarkhau/bumpver/issues/200
+
+
 ## BumpVer 2022.1120
 
 - Fix [#196][gh_i196]: Add `--pin-increments`.

requirements/pypi.txt

@@ -15,7 +15,9 @@ toml
 lexid
 colorama>=0.4
 
+# looseversion is needed to parse non PEP440 versions
+looseversion; python_version >= "3.5"
+
 # setuptools is needed for pkg_resources.parse_version
 # Support for Python 2 was dropped with v45
 setuptools<45.0.0; python_version < "3.5"
-setuptools>=45.0.0; python_version >= "3.5"

src/bumpver/version.py

@@ -11,9 +11,15 @@ MaybeInt = typ.Optional[int]
 
 def parse_version(version: str) -> typ.Any:
     # pylint: disable=import-outside-toplevel; lazy import to speed up --help
-    import pkg_resources
 
-    return pkg_resources.parse_version(version)
+    try:
+        import pkg_resources
+
+        return pkg_resources.parse_version(version)
+    except (ImportError, pkg_resources.extern.packaging.version.InvalidVersion):
+        import looseversion
+
+        return looseversion.LooseVersion(version)
 
 
 class V1CalendarInfo(typ.NamedTuple):